1. Field of the Invention
The invention pertains to the field of furniture. More particularly, the invention pertains to the field of chairs having extending feet or other supports.
2. Description of Related Art
The ergonomics of sitting for protracted periods requires regular changes in body posture. Rubber ball seats and spring-mounted chairs do not offer the body any possibility of rest and have to be constantly rebalanced. There are inventions for chairs which link backward tilting of the chair backrest with forward movement of the chair seat. In the case of the known inventions, the movement of the chair seat is normally effected by complicated systems of levers which, however, permit too little horizontal movement of the seat.
Especially for non-swivel chairs, this (synchronised) idea, although invented in these cases for other reasons, has long been known, e.g. Swiss patent CH 26 97 55. In this case, the seat and backrest, which are linked by a swivel joint, together with a top mounted supporting surface, can even be turned into a horizontal table, whereby the seat moves forward a long way and the backrest and supporting surface can be lowered until completely flat.
As a rule, however, the reason for the design of such synchronised chairs is to enable a comfortable sitting position to be achieved. An example for technology allowing (some) forward movement of the chair seat is shown for a swivel chair in European published patent application EP 0 460 717 A2, although in this case a bolt device is claimed as the patent for this movement. The backward tilt of the chair backrest, which is attached to the seat by a swivel joint, is made possible by the armrests, mounted movably on swivel joints, which serve as the main holding levers for the backrest. A tension spring mounted under the seat counteracts the weight of the occupant exerted on the backrest. The angle of the seat is thereby also changed slightly.
Another example of movable seat technology is shown in German patent application DE 33 15 237 A1. In this case, however, the backrest is held not by the armrests but directly in mounts on the base of the chair, as is also the seat, though this slides forward when the backrest is tilted.
In these known swivel chairs, however, the horizontal movement of the seat is intentionally kept very low as, with any greater forward movement, the chair with its occupant would be in danger of tipping forwards. Their inventors have, therefore, not produced designs which would allow the goals stated in the introduction to be genuinely achieved. The alternative would have been to reserve an enormous space on the floor to provide supporting feet for the chair, which has naturally not been done. Nor is it feasible to bolt office chairs to the floor. A magnetically switchable adhesion system would be the best alternative solution in this case, but the intended purpose would nevertheless not be achieved as the horizontal movement needs to be 30 to 35 cm to offset a tilt in the chair backrest of approx. 30 to 40 degrees. Rubber ball sets represent are only a makeshift solution as they do not solve the problem of distance, and with the need for the occupant to continually adjust his/her balance there is a risk of falling off. And while allowing different sitting positions, they do not have a backrest to provide support for the spine.
The objective is to design a chair which allows horizontal movement of the seat both without effort and without noise disturbance. At the same time, the benefits and dimensions of a normal swivel office chair should be preserved as far as possible, at least in the normal sitting position.
Various approaches can be adopted for achieving this objective. The base of a swivel (office) chair normally consists of five feet and the familiar gas spring mechanism for vertical height adjustment. The known approach to the technical task relating to the chair seat and backrest employs lever mechanics, combined with a (too) small sliding movement so as to prevent the center of gravity from moving too far forward.
A recognized benefit of changing sitting positions on a chair is achieved by new combinations of several elements, some of which are already known, but which through logical linking are made dependent on one another in respect of their movement. The position of the extended hand relative to the work desk remains almost unchanged while the seat moves backwards and forwards on the chair and the backrest tilts. The swivel chair retains its normal function as long as the backrest is not sharply tilted. When the linking is completely decoupled and the backrest is able to tilt without movement of the seat, the chair behaves like a normal chair.
The invention relates to linking an extending foot and the possibility of swiveling with tilting of the chair backrest synchronized with horizontal movement of the chair seat. It is intended for the linkage system to be installed on a swivel chair. With this (office) chair, it is intended to synchronize the tilt of the backrest with the forward movement of the seat in such a way that the distance of the seat occupant""s hands relative to the work equipment on the desk top remains virtually constant at all times.